I wholeheartedly agee with Gonglee3, cable is an issue. I looked up your other thread and saw you're not sure what cable you're presently using, we should try to find that out first. I presume you're living in the USA where you'll find loads of reasonably priced cables from brands that I have no personal experience with, however, such as Speltz Anti Cables or Morrow. Of the brands I do know myself, you could look at the likes of Kimber 4TC or Purist Vesta on Audiogon or usedcable. I have to point out one potential problem: you won't know what the cable does in your system until after you hooked it up. I would therefore think, you should have the question of a new amp out of the way first (btw you mentioned Rotel in your thread; if it's one of the more recent series, I believe that should be a nice match with the IQs), upon which you could get more precise advice e.g. by starting a thread here ;^).
I am not convinced bi-wiring is always a blessing (certainly not in recent years, where every cheapo box flashes double or triple binding posts as a sales pitch; sorry for ranting, this does absolutely not apply to your IQs but I had to get this off my chest). By the nature of it, it must be more expensive though. Good jumpers, or a bi-wiring adaptor may be at least equally satisfying.
I am a bit worried over your remark about bass quality as it flies in the face of test results to some extent. Your IQs will have their fair share of mileage, of course, are you sure the bass drivers are still OK? Another possible explanation may be that your present amp just cannot deliver the goods, the IQ's impedance curve dips a few times below 4 ohm. (Btw I would strongly advise against a solution where you continue to use your old HK as pre-amp.)
All of the above imho; hope I didn't sound too much "I'm the headmaster"-like.